Vitamin D could reduce the risk of diabetes

In a recent meta-analysis by Boston University, vitamin D reduced the risk of developing manifest type 2 diabetes by 15 percent in adults with prediabetes.

Vitamin D deficiency with high prevalence

High serum vitamin D levels reduce the risk of progression to type 2 diabetes

A systematic meta-analysis of three randomised clinical trials of vitamin D in diabetes prevention, recently published in the Annals of Internal Medicine, found that people with prediabetes who took vitamin D supplements had a 15 percent lower risk of developing manifest diabetes. Over a period of three years, the absolute risk reduction was 3.3 percent. The Number Needed to Treat (NNT) was 30. A total of just under 4,200 people were included in the analysis, which somewhat limits the statistical power for real conclusions on blood sugar control.2

"This relative risk reduction may seem small, but when extrapolated to the more than 374 million adults with prediabetes worldwide, it suggests that low-cost vitamin D supplementation could halt the progression of type 2 diabetes in more than 10 million people," the authors write.3

The three controlled trials were from Norway, the US and Japan and had randomised participants to the following doses or placebo: Cholecalciferol 20,000 IU weekly, 4,000 IU daily or Eldecalcitol 0.75 μg daily.

The meta-analysis reported no evidence of differences in adverse event rates (kidney stones RR 1.17; hypercalcaemia RR 2.34; hypercalciuria RR 1.65; death RR 0.85).

How much vitamin D is enough?

It is estimated that about 50 percent of the world's population is vitamin D deficient.1 While there are relatively clear figures and recommendations for other micronutrients, the situation with vitamin D is a little more complex and the individual daily requirement is more difficult to determine. Factors to consider include the state of body reserves (initial start of supplementation versus maintenance dose), time of year and age. Previous recommendations on vitamin D dosage have been strongly criticised for being too generalised and set far too low.4 They may often be just enough to prevent manifest deficiency (severe deficiency occurs at blood levels below 20 ng/ml). In order to achieve sufficient serum concentrations and not deplete the body's stores, a multiple of the previous low recommendations may sometimes be necessary.5,6

Adults need about 3,000 to 5,000 IU of vitamin D daily (from all sources combined: Sun, food and vitamin D from body stores).5 When supplementing, it must be taken into account that the oral bioavailability of most preparations is about 50 percent. For chronically ill people (such as MS patients), higher target ranges are usually recommended than for healthy people. Depending on the source, information of 60 to 90 ng/ml (150 to 225 nmol/L) is currently often found here, which is intended as a guide.7,8

Participants in the above-mentioned Norwegian study and the American study who maintained mean serum 25-hydroxyvitamin D levels ≥ 125 nmol/L had a 76 per cent lower risk of developing type 2 diabetes than those whose levels were between 50 and 74 nmol/L. The results of this meta-analysis suggest that prediabetics should maintain a 25-hydroxyvitamin D level close to or above 125-150 nmol/L (equivalent to 50-60 ng/ml).3

What to consider when taking high-dose vitamin D3

When substituting vitamin D, it is important to consider the rest of the micronutrient status and to take vitamin K2 and magnesium in addition to avoid complications related to excessive calcification.

Magnesium is necessary for the activation of vitamin D and without sufficient amounts of it, the vitamin D taken cannot be utilised correctly. This is of particular importance in this patient group, as poorly controlled diabetes can lead to magnesium deficiency. Conversely, prospective longitudinal studies have also documented that a deficiency of magnesium promotes the components of the metabolic syndrome.

But it is also a common and often neglected problem in the general population. More than half of the people are probably under-supplied here (depending on the source, there is a wide range of estimates). According to WHO figures, up to 75% of US Americans do not reach the recommended daily intake.9 You can read why it is so difficult to get enough magnesium in a standard Western diet and how to improve the situation - apart from supplementation - in the bottom half of this article on hypomagnesemia. If supplementation becomes necessary, magnesium L-threonate and magnesium transdermal (as oil) are considered the most usable forms for the organism.

Vitamin D should also be taken in combination with vitamin K2 (menaquinone), as the two work together and many patients are also deficient here. Vitamin K2 (not K1) is essential for the correct removal and utilisation of calcium and thus plays a particularly important role in the prevention of osteoporosis, arteriosclerosis and coronary artery disease. A K2 deficiency increases the risk of dying from heart failure almost as significantly as heavy smoking.5,6,10 All-trans menaquinone-7 (MK-7) is considered the most available and effective form for the body.

  1. Siddiqee, M. H., Bhattacharjee, B., Siddiqi, U. R. & MeshbahurRahman, M. High prevalence of vitamin D deficiency among the South Asian adults: a systematic review and meta-analysis. BMC Public Health 21, 1823 (2021).
  2. Pittas, A. G. et al. Vitamin D and Risk for Type 2 Diabetes in People With Prediabetes. Ann Intern Med (2023) doi:10.7326/M22-3018.
  3. Vitamin D May Slow Progression to Type 2 Diabetes. The Doctor Will See You Now
  4. Heaney, R. P. & Holick, M. F. Why the IOM recommendations for vitamin D are deficient. J Bone Miner Res 26, 455–457 (2011).
  5. In German only: Vitamin D Tagesbedarf | Dr. Schweikart.
  6. In German only: Höhere Vitamin D-Spiegel mit niedrigerem Krebs-Risiko assoziiert.
  7. In German only: annojordan. Das MRT zeigt: Vitamin D ist Pflichtprogramm gerade auch bei immunmodulierten Patienten. Life-SMS (2021).
  8. MS & Vitamin D Deficiency.
  9. Who is at Risk for Magnesium Deficiency?
  10. Cundiff, D. K. & Agutter, P. S. Cardiovascular Disease Death Before Age 65 in 168 Countries Correlated Statistically with Biometrics, Socioeconomic Status, Tobacco, Gender, Exercise, Macronutrients, and Vitamin K. Cureus 8, e748 (2016).

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